The National Day of Prayer (36 U.S.C. § 119)^[1] is an annual day of observance held on the first Thursday of May, designated by the United States Congress, when people are asked "to turn to God in prayer and meditation". Each year, the president signs a proclamation, encouraging all Americans to pray on this day.^[2] The modern law formalizing its annual observance was enacted in 1952, although it has historical origins to a mandate by George Washington, the first president of the United States.^[3][4][5]

Its constitutionality is being challenged in court by the Freedom From Religion Foundation after their first challenge was unanimously dismissed by a federal appellate court in April 2011.^[6][7][8]